A typical EAF-EMS system comprises an electric arc furnace (EAF) and an electromagnetic stirring system (EMS). The EAF is a furnace utilizing electric arc to melt metallic material. A typical EAF comprises one or more electrodes and a power supply system operatively connected to the electrodes. The EAF is further equipped with gas burners mounted on the sidewalls and arranged to provide chemical energy to the melt. Additional chemical energy is provided by means, e.g. lances, for injecting oxygen and carbon into the furnace. The operation of the electrodes is controlled by a control unit operatively connected to a power supply system. The power supplied to the electrodes thereby creating an arc is called arc power. The electrodes form an arc between the electrodes and the metallic material, i.e. solid metal (e.g. scrap) that has been loaded into the EAF. Thereby, a metallic material is melted and heated by the arc power and chemical energy from the oxygen injection. An electrode controlling system maintains approximately constant current and power input during the melting of the metallic material until the temperature of the metal melt reaches a target tapping temperature thereafter the metal melt is eventually tapped to a ladle furnace. On the surface of the metal melt, slag and smoke layers are formed.
During the melting process, the electromagnetic stirring (EMS) system is arranged to stir the metal melt in the furnace and comprises at least one electromagnetic stirrer including a stirring coil, a power supply system is operatively connected to the stirrer. The stirring coil is typically mounted outside a steel shell of the furnace. This coil generates a travelling magnetic field to provide stirring forces to the metal melt. The stirrer operates at a low frequency travelling magnetic field, penetrating the steel shell of the furnace and moving the melt in a way similar to a linear electric motor. Thus, a linear force is created by the travelling linear magnetic field acting on the melt in the furnace and provides a uniform temperature of the metal melt.
To tap the metal melt at a target tapping temperature is critical for energy consumption as well as advanced EAF control. Today, a temperature of metal melt in the electric arc furnaces is measured with a cartridge in order to obtain a measurement at a time point. There are several disadvantages with such a temperature measuring. Firstly, several temperature measurement trials normally need to be carried out before EAF tapping. These temperature trials may postpone the process time and also increase the cost of consumable probes. Secondly, performing such measuring is an unpleasant task for an operator since he has to face high temperature in a harsh environment while being equipped with bulky clothes.
Patent Application US 2012/0140787A1 discloses a method comprising operating a burner gun unit in a lance mode in which gas stream is guided with supersonic velocity into a furnace chamber. A surface of a metal melt is freely-blown by the gas stream, which is formed over a time period by oxygen-containing gas. To be able to measure temperature of the metal melt, a first gas including oxygen has to be switched over to a second gas that is an inert gas and thereafter the temperature of the metal melt is measured using a temperature measuring unit including a non-contact sensor.